1. Field of the Invention
This invention relates to a cooling means for an electrical rotating machine, and more particularly to a cooling means for an electrical rotating machine, which is equipped with a cooling air introducing means, for forcibly cooling a commutator unit.
A cooling means for an electrical rotating machine disclosed in Japanese Laid-open Patent Publication No. Sho 51-129,604 (dated Nov. 11, 1976) is such that substantially a cylindrical rocker for use in brush-holders is positioned in the outer circumferential portion of a commutator, and a screening plate is disposed between the rocker-attaching portion and the brush-holders. This arrangement enables to forcibly feed cooling air introduced from a single portion to the commutator uniformly over the entire area thereof.
However, a drawback has been encountered with the above mentioned device, in that, because a ventilation hole is provided on an extension of an axis of respective brush-holder, it is impossible to increase a circumferential length of the rocker from the strength point of view, with the failure to provide a diametrically sufficiently large ventilation hole. Because of a small ventilation hole, an increased ventilation resistance results, thus failing to provide a cooling effect required.
2. Description of the Prior Art
The cooling means of this type for an electrical rotating machine is also proposed by Japanese Laid-open Patent Publication No. 51-41,803 (Apr. 8, 1976). This cooling means is so arranged that a cooling air is introduced from a lateral portion of an end bracket, and fed to the commutator surface in the direction of brushes.
Furthermore, U.S. Pat. No. 3,673,447 (issued June 27, 1972) discloses a cooling means of the type described.
As well known, the cooling of an electric motor is particularly directed to a field coil and a commutator. For this purpose, various cooling systems are adopted, such as a forcibly cooling system by means of a fan, a cooling system by means of a heat-pipe, and a forcibly cooling system by means of a blower. Particularly the blower cooling system is most effective for effecting concentrated cooling of portions required, with satisfactory cooling performance.
The blower cooling system however is impractical for cooling a DC electric motor used in an electric automotive, because a limited loading space of the electric automotive can not afford to provide a ventilating and cooling air passage therein.